Sound operated relay



Jan, 1, 1946. J- w CONN 2,391,882

SOUND OPERATED RELAY Filed May 31, 1945 Fig Sound Amplifier In venfok Joseph W .Oonn

' A fforney Patented Jan. 1, 1946 UNITED STATES PATENT OFFICE SOUND OPERATED RELAY Joseph W. Conn, United States Navy Application May 31, 1945, Serial No. 596,948

7 Claims.

My invention relates to sound operatedrelays. More particularly, my invention relates to a, sound operated relay of the type adapted to control an electric current in response to the reception of a sound wave of selected characteristics. Y

An object of my invention is to provide a sound operated relay responsive to sound impulses of short duration and steep wave front characteristics with which an electric circuit may be changed from normal operation by one sound impulse and may subsequently be returned to normal operation by a second impulse similar to the first.

Further objects and advantages of my invention will be apparent from the following description when taken in. conjunction with the drawing, inwhich Fig. 1 is a diagrammatic view of a sound operated relay in accordance with the preferred embodiment of my invention.

As shown in Fig- 1, a microphone M, which is preferrably, of an inherently stable type sensitive to sounds of relatively high audio frequencies, such as a dynamic, piezo-electric crystal, or condenser microphone, is connected to the input circuit of a suitable audio frequency electronic amplifier II. The output of the amplifier is con-' nected to a differentiation circuit comprisin condenser l2 and resistance l3. One side of the amplifier output may be conveniently grounded as indicated. Movabl contact I4 of relay I5 is connected to the differentiation circuit and serves to complete a connection through stationary contact 16 to one plate I! of duo-diode electronic tube I8 when the relay is in the unexcited or dropped- ,out position. An opposing stationary contact I9 is arranged to complete an alternative circuit from movable contact l4 upon excitation of relay l5 after the movable contact l4 disengages from contact IE to cathode of tube 18. Plate 21, which is arranged to receive electrons from cathode 20 when a signal is applied to the cathode, is externally connected to cathode 22, which is arranged to give 011' electrons to plate I! when a signal is applied to the plate. The two connected elements, plate 2i and cathode 22, are connected to the grid 23 of triode tube 24.. A resistance 25 is connected from grid 23, cathode 22, and plate 2| to ground to form a load resistance for either diode section of tub i8, it being possible for only one section at a time to be conductive. Cathode 25 is connected to ground through variable resistance 21 which serves as a self-biasing resistance for tube 24. It may prove desirable in some applications to connect a condenser (not shown) across resistance 2'! as a filtering condenser. Plate 28 of triode tube 24 is connected through actuating coil 29 of relay Hi to the positive (3+) power supply terminal 30 of a suitable direct current power supply unit 3i, the negative terminal 32 of which is grounded. Power supply may be of the battery type or may consist of a transformer, rectifier and filter to convert availabl alternating current to suitable direct eur= rent. Suitable power must also be supplied to the heaters 33 and 3d of tubes 28 and it, respectively, and to the heaters of tubes in'the sound amplifier ii in a well known manner. The power for the plates of tubes in amplifier i i may be convenient- 1y provided as shown from th same terminal dd, or a separate terminal, of power supply unit 35. A gain control indicated as 35 may be provided for amplifier ll. In addition to the movable contact Hi and the two stationary contacts it and i 9, relay 1 5 is provided with switching mean operable by the relay coil for controlling an external circuit. \s an example, the relay is shown with a second movabl contact 35 engaging with stationary contact 31 when the relay is droppedout and engaging contact 38 when the relay picksup. This additional switching mechanism may be used to complete one external circuit and disconnect another each time the relay picks-up or drops-out to control external equipment.

In operation, a sharp handclap or similar audible or super-audible noise pulse is received bymicrophone I!) which is sensitive to high frequency audible or super-audible sounds, the sound impulse is converted into an electrical pulse of steep wave front characteristics, the pulse then being amplified by sound amplifier ii. Th amplified pulse is presented to the difierentiation circuit comprised of relatively low capacity condenser l2 and resistance Hi. It has been determined by experimentation that the time constant of this circuit should be of the order of 2 /2 microseconds which will result from the use of a condenser l2 of .0005 microfarad capacity and a 5000 ohm resistance [3. These values are intended to be exemplary only and may be substantially different, dependent upon the conditions of use of the apparatus. Only a pulse of the desired steep wave front, or of other desired characteristics for which the differentiation circuit is designed, will pass this difierentiation circuit. The pulse which contains components both positive and negative with respect to ground potential, will be applied throu h relay contacts i4 and I6 to plate I! of duo-diod tube la. The tube will be made immediately conductive for the posiable contacts M and 36, changing the connections from the differentiation circuit to tube It Various modifications of the equipment and of the circuit described may be made within the scope of, my invention. Obviously, two separate diode tubes may replace the duo-diode described. The difierentiation circuit will be equally efiective if applied between the microphone l and the amplifier ll. Alternatively, two differentiation circuits may be provided, one in the connection from contact I6 of the relay to plate ll of tube i8 and disconnecting contact 35 from stationary contact 31 to turn of! external equipment. At the same time, contact 86 engages stationary contact 38, which may be used to turn on external equipment. Self-biasing resistor 2? is adjusted to apply a positive potential to cathode 28 great enough to limit the plat current of the tube 2 to a value insumcient to cause pick-up of relay I5 from dropped-out position but low enough to cause sumcient plate current to fiow to prevent drop-out of relay l5 from picked-up position. It will be apparent that the potential between the grid 23 and ground will be substantially zero volts when duo-diode I8 is non-conductive because of the short-circuiting effect of resistance 25 on the very small grid current of grid 23. The positive cathode potential with respect to ground is therefore the equivalent of a negative bias on grid 23.

The connections to tube i 8 are so changed when a pulse has caused relay IE to pick-up that any subsequent pulse from the diflerentiation circuit will be applied through relay contacts i4 and I9 to cathode of tube It. The negative components of the pulse are rectified by cathode 20 and plate 28 resulting in electron fiow from cathode 20 to plate 21 and thence through resistor to ground. A negative potential is thus produced on the ungrounded end of resistor 25 and consequently on grid 23 of tub 2&. Tube 24 is thus biased toward cut-ofi, the plate current is substantially reduced, being insumcient now to holdin relay I5, the relay drops-out, returning the. circuit to original condition, the external equipment being turned on (or off) again. and the circult being ready to receive another pulse to again operate the relay.

It is contemplated that the relay of my invention may be used in numerous applications, in-

cluding the control of radio receivers to which it is particularly adaptable. when applied to a radio receiver, the apparatus may be arranged to disable the receiver in response to a sound impulse of steeper wave front characteristics than normally reproduced by ordinary radio loudspeakers, such as an impulse produced by a sharp clap of the hands or snap of the fingers, -or a sharp; brief, high pitched whistle, and to return the receiver to normal operating condition in response to a second sound impulse of similar characteristics. To accomplish the control of a receiver, the relay contacts 36 and 3! may be utilized to normally complete one of the essential circuits of the receiver, such as the circuit from the output circuit of the detector tube to the input circuit of the audio frequency amplifier, or the circuit from the audio frequency output transformer to the voice coil of the loudspeaker. Alternatively, normally open contacts 36 and 38, may be used to short circuit a grid resistance, a transformer, or the loudspeaker voice coil of the receiver upon actuation of the relay to picked-up position. Numerous other methods of disabling v will be apparent to those skilled in the art.

and the other in the connection from. contact It to cathode 20, and the differentiation "circuit shown connected to the amplifier output omitted. It may also prove desirable under some circumstances to merely insert in the circuit shown in Fig. 1 an additional differentiation circuit in the. connection to cathode 20 or in the connection to lat ll of tube It, or in the connection between the microphone ill and amplifier II. The noise level at the microphone and the frequency characteristics of the noise, the microphone, the sound amplifier, and the desired operating sound pulses will be determinative of the desirability for these modifications and may require the use of an integ'ratorcircuit instead of the differentiation circult if it is desired to cause operation in response to low frequency impulses instead of to those of high frequency. If, as in'the suggested use of the invention to control a radio receiver, the noise level changes in-volume and frequency charac-- will normally be 15 milliamperes. It may be desirable, however, to periodically adjust this plate current upward or downward to meet certain changed requirements of an individual installation. Under certain circumstances, it may also prove desirable to change the values of resistors l3 and. 25, particularly if different microphones, amplifiers, or tubes are substituted. It is entirely feasible to provide several microphones to receive operating impulses at several points if desired.

It will also be found possible to utilize the sound amplifier to amplify sound for other purposes simultaneously with its use in the circuit described, since the pulses which pass through the diiferentiator circuit must be of steeper wave front characteristics than those normally produced in music or speech. For this modification,

it will usually be desirable to insert a second differentiator circuit between the microphone provided for pulse pick-up and the amplifier input. In this manner only that part of the sound picked up by the microphone which contains the operating steep wave front pulse isapplied from the microphone to the amplifier. Th differentiator circuit connected to the output circuit of the amplifier will then serve to pass only the desired pulses to th elements of the duo-diode tube. other portions of the amplified signal, being unaffected, may be utilized as desired; It is accordingly possible to use the existing audio frequency amplifier of the radio receiver to be controlled as the sound amplifier for my invention.

While I have shown a particular embodiment of my invention, it will be understood, of course.

that I do not wish to be limited th'ereto, since many modifications may be made, and I, therefore, contemplate by the appended claims to covor any such modifications. as fall within the true spirit and scope or my invention.

The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

What is claimed is:

1. In a sound operated relay, a microphone, a thermionic control tube for said relay, at least a cathode, a control grid and an anode in said control tube, means for applying a positive electrical impulse to the grid of said control tube in response to a sound impulse received by said microphone to cause said relay to pick-up, and means operable by said relay as it picks-up to re condition said first-mentioned means for applyinc a negative electrical impulse to the grid of said control tube in response to a subsequent sound impulse received by said microphone to cause said relay to drop-out.

2. In a sound operated relay, a microphone, a thermionic control tube for said relay, at least a cathode, a control grid and an anode in said control tube, means for applying a positive electrical impulse to the grid of said control tube in response to a sound impulse received by said microphone to cause said relay to pick-up, means operable by said relay as it picks-up to recondition said first-mentioned means for applying a negative electrical impulse to the grid of said control tube in response to a subsequent sound impulse received by said microphone to cause said relay to drop-out, and a frequency selective device for preventing the application of electrical impulses other than those of predetermined frequency characteristics to the grid of said control tube.

3. In a sound operated relay comprising an actuating solenoid and a plurality of stationary and movable contacts operable thereby, a microphone, a duo-diode thermionic tube, and a grid controlled triode thermionic tube, said triode tube carrying a normal anode current of. less than full rated current, means including said microphone, one of said movable contacts, one of said one of said movable contacts, another of said stationary contacts, the other diode section of said duo-diode tube, and said grid controlled triode tube to decrease the current flowing through the solenoid below said normal triode current in response to the reception by said microphone of a second similar sound impulse to cause said relay to drop-out.

4. A sound operated relay operable by the anode current of a grid controlled thermionic control tube characterized by means, including a thenmionic diode and a microphone, for applying an electrically positive impulse when said relay is in dropped-out condition to the control grid of said control tube in response to the reception of a sound impulse by said microphone to cause the plate current of the control tube to increase to pick-up said relay, and a second means, including a second thermionic diode and said microphone, for applying an electrically negative impulse when said relay is in picked-up condition to the control grid of said tube in response to the reception of a sound impulse by said microphone to cause the plate current of the control tube to decrease todrop-out said relay, said firstmentioned means comprising a movable contact of said relay, a cooperating stationary contact, the anode and cooperating cathode of said first diode and a load resistance, said second means comprising said movable contact, another cooperating stationary contact, the anode and cooperating cathode of said second diode and said load resistance.

5. The combination with a relay of an actuating circuit for said relay comprising a, thermionic triode tube normally carrying an anode current less than full rated current, a first and a second thermionic diode, a microphone, a difi'erentiator consisting of a capacitor and a resistor for'passing electrical impulses of steep wave front characteristics from said microphone through an electric switch to the anode of said first diode to cause said first diode to draw unidirectional current; a load resistor connected to the cathode of said first diode arranged to produce a positive potential on the cathode in response to the current flow through said first diode, the anode of said second diode being connected to the cathode of said first diode, said switch being operable by said relay to disconnect the anode oi said first diode and to connect the cathode of the second diode to cause said impulses to be impressed on the cathode of the second diode instead of on the anode of the first diode, the anode of the second diode being arranged to draw current through said load resistor to produce a negative potential on the interconnected cathode of said first diode and anode of said second diode in response to conduction of said second diode initiated by the impression of an impulse on the cathode of the second diode, and an electrical connection for impressing the potential appearin on the interconnected elements on the grid of said triode tube to increase the anode current of said triode above normal value in response to the impression of an impulse on the anode of said first diode and to decrease the triode anode current below normal value in response to the impression of an impulse on the cathode of said second diode, said relay being operative into picked-up position by said increased triode anode current and operative into dropped-out position by said decreased triode anode current, the normal triode anode current being sufficient to maintain said relay in picked-up position but insufficient to cause said relay to pick-up from dropped-out position.

6. In a sound operated relay, the combination of a microphone, an electronic amplifier for amplifying the electrical output of said microphone, a movable switch contact operable by said relay into engagement alternatively with a first and a second stationary contact, a thermionic diode, a load resistor, an electrical connection from the anode of said diode to the first stationary contact and a connection from the cathode of said diode to one end of the load resistor, a ground connection to-the other end of the resistor, a second thermionic diode, a connection from the cathode of the second diode to the second stationary contact and aconnection from the anodeof the second diode to said one end of the load resistor, an operating solenoid coil for the relay effective when excited by more than a, predetermined pick-up current to pick-up the movable contact into engagement with the second stationary contact, biasing means for moving the said one end .01 the load resistor to the control grid to cause an increase in anode current of the control tube which will result in picking-up of the movable contact upon conduction by theflrst diode and to cause a decrease in anode current of the control tube which will result in droppingout of the movable contact. upon conduction by movable contact into engagement with the first stationary contact when the operating solenoid coil is excited by less than a predetermined dropout current, said drop-out current being substantially less than said pick-up current, means for applying at least a portion of th electrical out-. put of the microphone to the movable contact to cause said first diode to conduct when the movable contact is in dropped-out position and to cause said second diode to conduct when the mov- Certificate of Correction the second diode, and a difierentiation circuit in a connection. between the microphone and at least one of thosediode elements which are not connected to said one. end of the load resistor,

the diflerentiation circuit comprising a resistor and a condenser.

7. In a sound operated relay, the combination of a thermionic control tube, means to-appl an electrical impulse to an element of said control tube to increase the conductance of said control tube, modifying means for modifying said firstmentioned means to apply a subsequent electri cal impulse to decrease the conductance of said control tube,'means for operating said relay in accordance with the conductance of said contr l tube, and modifying means constituting a tion of said relay.

I JOSEPH W. CONN.

January 1, 1946.

por-

Patent No. 2,391,882. I

4 JOSEPH W. CONN It is hereby certified that error appears in the printed specification of the above numbered patent requirin correction as follows: Page 4, second column, line 23, claim 7, for the words an modifying read said modifying; and that the said Letters Patents should be read with this correction therein that the same may conform to the record of the case in the Patent Oflice.

Signed and sealed this 6th day of August, A. D. 1946.

LESLIE FRAZER,

First Assistant Oommz'ssz'oner of Patents. 

